For internal combustion engines, it is essential to avoid extreme operating points of the engine such as heavy knock and misfire. Heavy knock causes rapid pressure oscillations of excessive magnitudes which potentially lead to a total breakdown of mechanical components. Cylinder misfire again increases emissions significantly and is potentially harmful for catalysts. In addition, for gas engines it is essential to cut-off the fuel supply to a misfiring cylinder, as the gas otherwise flows to the exhaust-gas pipe and explodes.
A multiple cylinder gas engine or a multiple cylinder diesel engine for power generation incorporates a control for stopping the engine when abnormal combustion, for example heavy knock, occurs in one or more cylinders.
In a conventional internal combustion engine, when continuous heavy knock occurs in one of the cylinders in a normal operating condition, the supply of fuel into all of the cylinders is cut off so as to stop the engine after a predetermined time elapses from the time of detection of the heavy knock. The engine merely comes to a stop after the detection of occurrence of heavy knock in order to protect the engine.
A patent document JP11093757A discloses solution to prevent the pre-ignition by detecting a knocking as the occurrence of a pre-ignition when the knocking is continued over a prescribed period regardless of the suppression of knocking by the control of fuel parameter when the knocking is detected, and reducing the output of the corresponding cylinder. In JP11093757, no consideration is made for detailed control for operation of fuel cut off of an engine upon occurrence of abnormal combustion.
WO 2008038827A1 discloses an operation method of an engine during abnormal combustion in which operation control of the engine can be performed appropriately after fuel supply interruption to a heavy knock-inflicted cylinder without stopping the engine immediately upon detection of occurrence of heavy knock. In WO 2008038827A1, no consideration is made for detailed control for operation of fuel cut off of an engine upon occurrence of abnormal combustion.